Throttle body failure or not??

[sfcl]

Hi all,
I described my problem on this forum some days ago (thanks again Waesel!) as a probable throttle body failure as my Peake scanner displayed more and more often the code 88 (table 19) so a "Throttle position sensor, adaptation selftest". I finally showed the car to the local BMW agent (remember, I'm in the islands so no big BMW dealer here...) and he says that he doubt that it is the cause of the failure and he suggest to let the car so he can check. I'm quite confused now!
Giving that I wouldn't like to pay hundreds bucks for just a check, still without knowing exactly where is the problem I guess, maybe you can help me a bit more?

The problem: It occurs only at very low engine rpm, means when the engine is at idle speed or when the throttle pedal is very slightly pushed.

- If it is at idle, the engine runs well for some minutes then begins to misfire and finally stalls. The check engine soon light comes on when the misfires occur. Ther EML light and limp mode don't occur all the time, sometimes yes, sometimes not.

- If it is at low throttle openings, the engine speed varies, means it passes from (for example) 1200 to 1500, then 1200, then 1500 all the time every second (means the engine speed varies - pulses- by about 300 or 400 rpm ebvery second or so). Then the check engine light somes on, and sometimes only the EML light and limp mode.
Most of the time however, the limp mode and EML light only occur when I restart the engine after a stop.

If I run the engine at high engine speed (above 2000 rpm) so most of the time on open roads, there is absolutely no problem, the engine runs fine and strong. This means that the problem occurs only if the engine idles or at very low speed, so only in trafic or in town.

Noticed that sometimes I get 2 codes with the Peake scanner: 88 (Throttle position sensor, adaptation selftest) and 73 (Throttle position sensor, adaptation).

What do you think? Does you think that the throttle body in the only cause (I would have thought that a failure in the throttle body would affect the whole range and not only the low speeds)?
Thanks in advance for you help!

[sfcl]

Sorry, I forgot to mention that it is a 3.0I engine, 2001 model.

[sfcl]

Any idea everyone? Sorry for my bad english, just ask if it is not clear.

[munchkin29483]

This may sound off the wall but I had the same problem with my 1994 Pathfinder that has since been replaced with my 2006 X5. (lucky Grandson got the PF for free, 223K miles on the old girl)
Too make a long story short, the problem turned out to be a bad spark plug. The machine would idle rough and stall on the low end and above 2000 RPM it would run like a top.

[sfcl]

The spark plugs are new, this was the first job I did since the problem occured. Thanks for the reply anyway.

[Laurence]

If the throttle position sensor is faulty or intermittent the engine management system will not know how far open or closed the throttle actually is.
If the management system is getting random or intermittent information it can cause all sorts of issues. In your case, at idle, if the throttle position sensor is giving the management system random or intermittent information, the resulting engine fuelling will be incorrect i.e. too rich, which could well cause the engine to stall.
It is also quite possible for a throttle position sensor to wear more in the closed throttle area; this could explain why you only see this problem at low speeds.

This is not meant to be a complete diagnosis, more of a rational explanation of why you would see this engine behaviour. If it were me, I would start with the throttle body.

[Weasel]

How much would the guys diagnosis be? The throttle body will be about $450 just in parts, then the throttle adaptations should be cleared using the GT1 after replacement. If the diagnosis is just ~$100 and it turns out to be something cheaper like the idle control valve sticking it will be worth it. I just don't like seeing people spend multiple times more on parts that weren't the cause of the problem than just paying a one time diagnosis fee.

[sobi6111]

Had same thing,and BMW replaced the throttle body and all the wiring and reprogrammed ECU. Was about 1700$ fix :-( with parts and labor and 3 year warranty for it.

[sfcl]

Thanks all for your reply.
Problem here is not really the cost of the diagnosis, it is that whatever the cost I'm not sure at all that they will do a good diagnosis! Last time I had to bring the car to them was for a EML, brakes and another yellow (can't remember which one) lights + limp mode, they diagnosed a fried ABS module and it was only an ABS sensor on the front LHS wheel...
Same for a problem of fuel gauge, they advised to change the 2 sensors on the fuel tank and it was only the small o-ring (splitted) on one of the sensor (so the fuel can't pass from a tank to the other).
In other words, each time I have to solve a problem I'm trying to collect as much information as I can before taking a decision. I'm of the opinion that some of you on this forum have a better knowledge that some BMW dealers...

[sobi6111]

Originally Posted by sfcl

Thanks all for your reply.
Problem here is not really the cost of the diagnosis, it is that whatever the cost I'm not sure at all that they will do a good diagnosis! Last time I had to bring the car to them was for a EML, brakes and another yellow (can't remember which one) lights + limp mode, they diagnosed a fried ABS module and it was only an ABS sensor on the front LHS wheel...
Same for a problem of fuel gauge, they advised to change the 2 sensors on the fuel tank and it was only the small o-ring (splitted) on one of the sensor (so the fuel can't pass from a tank to the other).
In other words, each time I have to solve a problem I'm trying to collect as much information as I can before taking a decision. I'm of the opinion that some of you on this forum have a better knowledge that some BMW dealers...

Try to clean throttle body maybe? or unplug wiring from throttle and use contact cleaner maybe? It is the cheapest you can do yourself,if no help. then probably it is really throttle body itself,or wiring. or maybe coding error.